Cetyl myristoleate (CMO) is the common name for hexadecyl cis-9-myristoleate. CMO is the ester of cis-9-tetradecenoic acid (myristoleic acid) and 1-hexadecanol (cetyl alcohol). Cetyl myristoleate is well known for its anti arthritis properties. Hexadecyl cis-9-tetradecenoate was found only in very selective number of species of animals including cows, whales, beavers and mice. Cetyl myristoleate was isolated from mice in 1972 by Harry W. Diehl, a researcher at the National Institutes of Health (Diehl H W, May E L. J Pharm Sci 1994; 83:296-9). Cetyl myristoleate has been used for immunizing against inflammatory rheumatoid arthritis in mammals (Diehl, U.S. Pat. No. 4,049,824, Levin, WO 01/41783), treatment of rheumatoid arthritis (Diehl, U.S. Pat. No. 4,113,881) and osteoarthritis (Diehl, U.S. Pat. No. 5,569,676). Vegetable butter-based cetyl myristoleate was also used for treating osteoarthritis and other musculoskeletal disease conditions and injuries (Leonard, US 20030181521). Nutraceuticals containing CMO are widely used for reducing pain inflammation, and with the exception of a report suggesting a positive clinical effect of cerasomol-CMO in patients with fibromyalgia (Edwards A M. J. Nutr. Environ. Med. 2001; 11:105-11). As Swiss Albino Mice is the only natural source for CMO, Kenneth et al, synthesized pure hexadecyl cis-9-tetradecenoate by esterifying cis-9-tetradecenoic acid (purchased from commercial source) with 1-hexadecanol by chemically and confirmed its anti arthritic properties in a collagen-induced arthritis model in DBA/1 Lac J mice (Kenneth W. Hunter, Jr., Ruth A. Gault, Jeffrey S. Stehouwer, Suk-Wah Tam-Chang. Pharmacological Research 2003; 47:43-47). cis-9-Myristoleic acid is naturally available as a mixture of fatty acids along with other fatty acids in beef tallow fat with cis-9-myristoleic acid content of 8% (Lord G, WO 00/64436) and seed fat of Pycnanthus Komb with 20-30% of cis-9-myristoleic acid (Leonard, US 20030181521). Literature search revealed that there is no synthetic route reported for the preparation of cis-9-myristoleic acid. Since the natural availability of cis-9-myristoleic acid is scarce, the present invention reported synthetic route for the first time from methyl oleate. As it is difficult to isolate pure oleic acid from any vegetable oil source, the present invention reported the synthesis of a new isomer cis-10-myristoleic acid for the first time from commercially available raw material namely, undecenoic acid. Cetyl myristoleate was then prepared by transesterifying both methyl cis-10-myristoleate and cis-9-myristoleate separately with cetyl alcohol and evaluated for anti-inflammatory and anti-arthritis activity. The anti-inflammatory and anti-arthritis properties of the new isomer i.e. cetyl cis-10-myristoleate was compared with that of known CMO containing cis-9-myristoleic acid prepared as described above.
The first step of the synthetic route is preparation of cis-9-myristoleic acid from oleic acid. Oleic acid is not available in pure form, and has to be prepared from oleic acid-rich oils like olive oil by employing methodologies like urea adducts or fractional distillation. As the isolation of pure oleic acid from natural sources is very expensive, the cost of cetyl myristoleate based on cis-9 myristoleic acid will also be very high. Hence, there is a need for the identification of an alternate source of myristoleic acid for the preparation of CMO. Surprisingly, not much work was reported in this direction either for the chemical synthesis of cis-9 myristoleic acid or any other alternate raw material for the preparation of CMO. Keeping these points in view, the present invention explored the possibility of synthesis of alternative isomers of myristoleic acid, for the preparation of cetyl myristoleate. An attractive substrate in this direction is 10-undecenoic acid for the preparation of cis-10 myristoleic acid. 10-Undecenoic acid is a pyrolysis product of castor oil fatty acid methyl esters (methyl ricinoleate) and is commercially available in bulk in pure form. In the present invention, both the isomers of methyl esters of cis-9 and cis-10 myristoleic acids (3 and 7) were prepared from oleic and undecenoic acid methyl esters and further transesterified with cetyl alcohol to obtain hexadecyl cis-9-tetradecenoate, 4 and hexadecyl cis-10-tetradecenoate, 8. Both hexadecyl cis-9-tetradecenoate, 4 and hexadecyl cis-10-tetradecenoate, 8 were evaluated for anti-arthritis properties and found that hexadecyl cis-10-tetradecenoate, 8 is comparable with that of hexadecyl cis-9-tetradecenoate, 4 in inhibiting inflammation and effective in adjuvant-induced arthritis in rats.